1,2,3,4-tetrahydro - 2 - nitroso - 9h-pyrido (3,4-b)-indole-3-carboxylic acid



United States Patent ()fifice 3,476,764 1,2,3,4-TETRAHYDRO 2 NITROSO 9H-PYRIDO [3,4-b]-INDOLE-3CARBOXYLIC ACID Hans A. Wagner, Skokie, Ill., assignor to G. D. Searle & Co., Chicago, 11]., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 681,897, Nov. 9, 1967. This application Dec. 4, 1967, Ser. No. 687,480

Int. Cl. C07d 57/04, 85/50; A0111 9/22 U.S. Cl. 260295 3 Claims ABSTRACT OF THE DISCLOSURE Preparation of 1,2,3,4-tetrahydro-2-nitroso-9H-pyrido- [3,4-b]indole-3-carboxylic acid and meso-ionic didehydro 3a,4,9,l0 tetrahydro 1H,3H [1,2,3]oxadiazolo [3,- 4':1,6]pyrido[3,4-b]indol 3 one intermediates to pepsin-inhibiting and anti-ulcerogenic 9,10-dihydro-4H-pyrazolo[1',5':1,6]pyrido[3,4 b]indo1e 2,3 dicarboxylic acids and esters are disclosed.

and

wherein Z represents an alkyl, cycloalkyl, cycloalkenyl, aralkyl, or optionally-substituted phenyl radical.

Among the alkyl radicals represented by Z, lower alkyl radicals are preferred, i.e., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, isohexyl, heptyl, or like monovalent, saturated, acyclic, straightor branched-chain, hydrocarbon grouping of empirical formula wherein n represents a positive integer less than 8.

The cycloalkyl radicals represented by Z are typified by cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and the cycloalkenyl radicals represented thereby are, specifically, those derived from the aforesaid cycloalkyl radicals by elimination of 2 hydrogens to give rise to an endocyclic double bond Among the cycloalkyl and cycloalkenyl radicals represented by Z, the cyclohexyl and A A or A cyclohexyli.e., cyclohexenylgroupings are preferred.

The aralkyl radicals represented by Z are preferably those comprising a methyl grouping substituted by phenyl wherein a second phenyl or a lower alkyl grouping can also be substituted. Illustrative of such radicals are benzyl,

3 ,476,764 Patented Nov. 4, 1969 u-methylbenzyl, u-ethylbenzyl, a-isopropyl-benzyl, diphenylrnethyl, etc.

The optionally-substituted phenyl radicals represented by Z are preferably phenyl and phenyl substituted by a lower alkoxy grouping or halogen. Those skilled in the art will recognize that lower alkoxy groupings have the formula Olower alkyl wherein lower alkyl is defined as before. The halogens embraced by Z are most desirably those of a atomic number greater than 9 and less than 53i.e., chlorine and bromine. Positioning of the lower alkoxy or halo substituent about the benzene ring is not critical, 0-, m-, and p-substituted phenyl groupings alike being contemplated.

Inasmuch as there is at least 1 asymmetric carbon atom present in each of the compounds of this invention, the compounds exist both as racemates and the stereochemically homogeneous isomers which compose them. Compopnds in which 2 asymmetric carbon atoms are present, such as the products of Example 7 hereinafter, commonly occur as mixtures of racemates separable, as illustrated, by fractional crystallization.

The compounds to which this invention relates are useful not only as intermediates but also are characterized by valuable pharmacological properties. Thus, for example, they are, variously, pepsin-inhibiting, anti-ulcerogenic, hypocholesterolemic, anti-microbial in respect of bacteria such as Diplo coccus pneumoniae, anti-inflammatory, and adapted to prevent dicotyledenous seed germination.

Preparation of the instant intermediates and 9,10-dihydro 4H pyrazolo[l',5:l,6]pyrido[3,4 b]indole 2,3- dicarboxylic acids and esters derived therefrom proceeds by contacting an acetic acid suspension of an appropriate 1,2,3,4 tetrahydro 9H pyrido[3,4 b]indole 3 carboxylic acid [Z being defined as above] with cool aqueous sodium nitrite to give the corresponding 2-nitros0 compound, which, upon heating with acetic anhydride, affords the corresponding meso-ionic didehydro 3a,4,9,10 tetrahydro 1H,3H [l,2,3]oxadiazolo[3, 4- 1,61-pyrido [3,4-b] indole 1 lam,

[Z being defined as above] The latter compound is heated with an appropriate dialkyl acetylenedicarboxylate in ethylene glycol diethyl ether [Diethyl Cellosolve] to give the corresponding 9,10-dihydro 4H pyrazolo[l',5':l,6]pyrido[3,4-b]indole 2,3-

- dicarboxylic acid ester, from which the free acid is 0btained by saponification with hot aqueous methanolic potassium carbonate.

The following examples describe in detail compounds illustrative of the present invention and methods which have been devised for their preparation. It will be apparent to those skilled in the art that many modifications, both of materials and of methods, may be practiced without departing from the purpose and intent of this disclosure. Throughout the examples hereinafter set forth, temperatures are given in degrees centigrade and relative amounts of materials in parts by weight, except as otherwise noted.

EXAMPLE 1 A. 1,2,3,4-tetrahydro2-nitroso-9H-pyrido- [3,4-b]indole-3-carboxylic acid To a suspension of 650 parts of 1,2,3,4-tetrahydro-9H- pyrido[3,4-b]indole-3-carboxylic acid in 4000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 235 parts of sodium nitrite in 400 parts of water. Stirring is continued 15 minutes longer, whereupon the resultant solution is mixed with decolorizing charcoal and filtered through diatomaceous earth. The filtrate is poured into 25,000 parts of ice-cold water, precipitating a yellowish solid which is filtered oflf, washed with water, and dried in air. The product thus isolated is l,2,3,4-tetrahydro 2 nitroso 9H pyrido[3,4-b]indole 3 carboxylic acid melting at 176178 with decomposition.

B. Meso-ionic didehydro 3a,4,9,10-tetrahydro-lH,3I-I- [1,2,3] oxadiazolo[3,4': 1,6] py1ido[3,4-b]indol-3-one A suspension of 50 parts of 1,2,3,4-tetrahydro-2-nitroso- 9H-pyrido[3,4-b]indole-3-carboxylic acid in 210 parts of acetic anhydride is stirred at 60-65 for 1% hours, during which time solution occurs. The solution is allowed to cool to room temperature during 2 hours, resulting in the formation of a crystalline precipitate. The mixture is poured into 2500 parts of water, and stirring is thereupon resumed for 3 hours. Insoluble solids are filtered off, washed on the filter with water, dried in air, slurried in hot methanol, reisolated by filtration, and Washed on the filter with a mixture of cold methanol and ether to give meso-ionic didehydro 3a,4,9,l0 tetrahydro lH,3H [1,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indo1-3-one melting at 247-250 with decomposition.

C. Dimethyl 9,10-dihydro-4H-pyrazolo[1',5: 1,6 pyrido- [3,4-b]indole-2,3-dicarboxylate A suspension of 227 parts of meso-ionic didehydro 3a,- 4,9,10 tetrahydro lH,3H [l,2,3]oxadiazolo[3,4':1,6]- pyrido[3,4-b]indol-3-one in a mixture of 155 parts of dimethyl acetylenedicarboxylate with 1500 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 2% hours. Carbon dioxide is liberated and solution occurs in process. The solution is allowed to stand at room temperatures overnight, whereupon precipitation occurs. The precipitate, filtered off and recrystallized from acetone, aifords dimethyl 9,10-dihydr-4H-pyrazolo- [1,5': 1,6] pyrido[3,4-b] indole-2,3-dicarboxylate melting at 253-255 The product has the formula COOCHa EXAMPLE 2 9,l0-dihydro-4H-pyrazolo[1',5: 1,6] pyrido [3 ,4-b] indole-2,3-dicarboxylic acid To a suspension of 65 parts of dimethyl 9,10-dihydro- 4H pyrazol0[1',5:1,6]pyridol[3,4-b]indole 2,3 dicarboxylate in 1000 parts of methanol is added a solution of 60 parts of potassium carbonate in 250 parts of water. The resultant mixture is heated at the boiling point under reflux for 4 hours, then poured into 5000 parts of cold water. The solution which eventuates is stirred with decolorizing charcoal and filtered. The pH of the filtrate is adjusted to 4 with dilute hydrochloric acid, inducing precipitation of a crystalline solid which is isolated by filtration, washed with water, dried in air, Washed by trituration with hot methanol, and again dried in air to give 9,10dihydro-4H-pyrazolo[1,5: 1,6] pyrido 3 ,4-b] indole-2,3-dicarboxylic acid ,melting at 250-253 with decomposition. The product has the formula N COOH I 'COOH EXAMPLE 3 A. 1,2,3,4-tetrahydro-l-methyl-2-nitroso-9H-pyrido- [3,4-b]indole-3-carboxylic acid Substitution of 690 parts of 1,2,3,4-tetrahydro-l-methy1-9H-pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,- 4-tetrahydro 9H pyrido[3,4-b]indole 3 carboxylic acid called for in Example 1A affords, by the procedure there detailed, 1,2,3,4-tetrahydro-l-methyl-2-nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid melting at approximately 183-184" with decomposition.

B. Meso ionic didehydro 3a,4,9,l0 tetrahydro 10- methyl lH,3H [1,2,3]oxadiazolo[3',4':1,6]pyrido- [3,4-b]indol-3-one Substitution of 53 parts of 1,2,3,4-tetrahydro-l-methyl- 2 nitroso 9H-pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4 tetrahydro-Z-nitroso-9H-pyrido-[3,4-b]indole- 3-carboxylic acid called for in Example 1B affords, by the procedure there detailed, meso-ionic didehydro 3a,4,9,l0- tetrahydro l0 methyl lH,3H [1,2,3]oxadiazolo- [3,4':l,6]pyrido[3,4-b]indol-3-one. The product decomposes at approximately 250 without melting.

C. Dimethyl 9,10 dihydro 10 methyl 4H pyrazolo- [1,5: 1,6] pyrido [3,4-b]indole-2,3-dicarboxylate I N ooocm COOCH:

EXAMPLE4 9,10-dihydro-l0-methyl-4Hpyrazolo[1,5': 1,6]- pyrido [3,4-b]indole-2,3-dicarboxylic acid Substitution of 68 parts of dimethyl 9,10-dihydro-l0- methyl 4H pyrazolo[1',5':1,6]pyrido[3,4-b]indole-2,3- dicarboxylate for the dimethyl 9,10-dihydro-4H-pyrazolo [1,5:1,6]pyrido[3,4-b]indole-2,3-dicarboxylate called for in Example 2 affords, by the procedure there detailed 9,10- dihydro-10-methyl-4H-pyrazolo[1',5: 1,6] pyrido 3,4 b] indole-2,3-dicarboxylic acid melting at approximately 275276. The product has the formula N 00011 L% H EXAMPLE 5 A. l-cyclohexyl-l,2,3,4-tetrahydro-9H-pyrido [3,4-b]indole-3-carboxylic acid To a solution of 817 parts of L-tryptophan in a mixture of parts of 96% sulfuric acid and 5000 parts of water is added a solution of 493 parts of cyclohexanecarboxaldehyde in 5000 parts of ethanol. The resultant solution is heated at the boiling point under reflux in a nitrogen atmosphere for 17 hours, whereupon 4000 parts of concentrated ammonium hydroxide followed by 20 parts of decolorizing charcoal is slowly introduced Heating at the boiling point under reflux is resumed for 10 minutes, at which point the mixture is filtered hot. The filtrate is diluted with 2000 parts of concentrated ammonium hydroxide and allowed to cool. The crystalline precipitate thrown down is l-cyclohexyl-l,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid which, filtered off, washed well with water, and dried in air, melts at 202-204.

B. l-cyclohexyl-l,2,3,4-tetrahydro-2-nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid To a suspension of 463 parts of 1-cyclohexyl-l,2,3,4- tetrahydro-9H-pyrido[3,4-b]indole-3 carboxylic' acid in 3000 parts of acetic acidat 15 is added, during 30 minutes with stirring, a solution of 117 partsof sodium nitrite in 300 parts of water. Stirring is continued 15 minutes longer, whereupon the resultant solution is treated with decolorizing charcoal and filtered. The filtrate is poured into 20,000 parts of ice-cold water, precipitating a yellowish solid which is filtered off, washed with water, and dried in air. The product thus isolated is l-cyclohexyl-1,2,3,4- tetrahydro 2 nitroso 9H pyrido[3,4-b]indole-3-carboxylic acid.

C. Meso ionic didehydro 10 cyc10hexyl-3a,4,9,lO-tetrahydro 1H,3H [1,2,3]oxadiazolo[3,4:1,6]pyrido- [3,4-b]indol-3-one A solution of 43 parts of l-cyclohexyl-l,2,3,4-tetrahydro-2-nitroso-9H-pyrido[3,4-b]indole-3-carboxylic acid in 270 parts of acetic anhydride is heated to 50 with stirring, whereupon heating is discontinued while stirring is maintained for 2 hours longer. The resultant mixture is poured into 2000 parts of water. The mixture thus obtained is stirred for 3 hours, whereupon insoluble solids are filtered olf, washed with water, dried in air, and further Washed by slurrying in hot methanol. The resultant product is mesoionic didehydro l cyclohexyl 3a,4,9,l0-tetrahydro-1H, 3H [1,2,3]0xadiazolo[3,4: 1,6] pyrido[3,4 b]indol 3- one melting at 2142l6.

D. Dimethyl l0 cyclohexyl 9,10-dihydro-4H-pyrazolo- [1,5' 1,6] pyrido [3 ,4-b indole-2,3-dicarboxylate A suspension of 232 parts of meso-ionic didehydro l0- cyclo hexyl 3a,4,9,10 tetrahydro lH,3H-[l,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indol- 3 one in a mixture of 116 parts of dimethyl acetylenedicarboxylate with 2000 parts of ethylene glycol diethylether is heated at the boiling point under reflux for 5 hours. Solvent is removed from the resultant solution by vacuum distillation. The residue is chromatographed on silica gel, using benzene and ethyl acetate as developing solvents. From an eluate comprising 20% ethyl acetate in benzene, on evaporation of solvent, dimethyl cyclohexyl 9,10 dihydro 4H-pyrazolo- [1,5': 1,6] pyrido[3,4 b]indole 2,3 dicarboxylate is obtained as the residue. The product has the formula N OOOCHz -cooorn 6 EXAMPLE 6 A. 1(3-cyclohexenyl)-1,2,3,4-tetrahydro-9H-pyrido- [3,4-b]indole-3-carboxylic acid Substitution of 484 parts of 3-cyclohexene-l-carboxaldehyde for the cyclo-hexanecarboxaldehyde called for in Example 5A alfords, by the procedure there detailed, l- (3 cyclohexenyl) l,2,3,4-tetrahydro-9H-pyrido[3,4-b1- indole-S-carboxylic acid melting at 193-195 with decomposition.

B. l-(3-cyclohexenyl)-l,2,3,4-tetrahydro-2-nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid Substitution of 460 parts of l-(3'cyclohexenyl)-1,2,3, 4 tetrahydro 9H pyridol[3,4 b]indole 3 carboxylic acid for the l-cyclohexyl-l,2,3,4-tetrahydro-9H- pyrido[3,4-b]indole-3-carboxylic acid called for in Example 5B affords, by the procedure there detailed, l-(3- cyclohexenyl)-1,2,3,4-tetrahydro-2-nitroso-9H pyrido[3, 4-b]indole-3-carboxylic acid.

C. Meso-ionic didehydro 10-(3-cyclohexenyl)-3a,4,9,l0- tetrahydro 1H,3H [1,2,3] oxadiazolo [3,4:l,6]- pyrido[3,4-b]indol-3-one Substitution of 43 parts of 1-(3-cyclohexenyl)-l,2,3,4- tetrahydro-2-nitroso-9H-pyrido[3,4-b]indole-3 carboxylic acid for the l-cyclohexyl-l,2,3,4-tetrahydro-2-nitroso- 9H-pyrido[3,4-b]indole-3-carboxylic acid called for in Example 5C affords, by the procedure there detailed, mesoionic didehydro l0-(3-cyclohexenyl)-3a,4,9,10-tetrahydro- 1H,3H-[l,2,3]oxadiazolo[3',4:1,6]pyrido[3,4, b]indol- 3-one melting at 216-218 with decomposition.

D. Dimethyl 10-(3-cyclohexenyl)-9',l0-dihydro-4H-pyrazolo[1,5: 1,6] pyrido [3 ,4-b] indole-2,3-dicarboxylate Substitution of 230 parts of meso-ionic didehydro l0- (3 cyclohexenyl) 3a,4,9,10 tetrahydro lH,3H-[l,2, 3]oxadiazolo[3,4:1,6]pyrido[3,4-b]indol 3 one for the mesa-ionic didehydro 10-cyclohexyl-3a,4,9,IO-tetrahydro lH,3I-I [l,2,3]oxadiazolo[3,4':1,6]py1'ido[3,4- b]indol-3-one called for in Example 5D affords, by the procedure there detailed, dimethyl 10-(3-cyclohexenyl)- 9,10-dihydro 4H pyrazolo[1',5:l,6]pyrido[3,4-b]indole-2,3-dicarboxylate which recrystallized from a mixture of acetone and n-pentane, melts at 186-188. The product has the formula EXAMPLE 7 10- (3-cyclohexenyl) =9, 10-dihydro-4H-pyrazolo[ l',5' 1,6]pyrido [3,4-b]indo1e-2,3-dicarboxylic acid A mixture of 81 parts of dimethyl 10-(3-cyclohexenyl)- 9,10 dihydro 4H pyraz0lo[1',5:l,6]pyrido[3,4-b] indole-2,3-dicarboxylate and 60 parts of potassium carbonate with 900 parts of methanol and 300 parts of water is heated at the boiling point under reflux for 2 hours and then stirred into 7500 parts of water. The resultant mixture is let stand at around 5 overnight, at which point insoluble solids are filtered off, washed with ice-cold water, dried in air, and extracted with 20 volumes of boiling methanol. The material which remains insoluble is filtered out, consecutively washed with methanol and ether, and dried in air. The product thus isolated is 10- (3 cyclohexenyl) 9,10 dihydro 4H pyrazolo[l',

':1,6]pyrido [3,4-b]indole-2,3-dicarboxylic acid melting at 282284, and having the formula EXAMPLE 8 A. 1,2,3,4-tetrahydro-2-nitroso-1-phenyl-9H-pyrido[3,4- b]indole-3-carboxylic acid To a suspension of 450 parts of 1,2,3,4-tetrahydro-1- phenyl-9H-pyrido[3,4-b]indole 3 carboxylic acid in 2000 parts of acetic acid at is added, during minutes with stirring, a solution of 127 parts of sodium nitrite in 200 parts of water. The resultant solution is mixed with decolorizing charcoal, the mixture is filtered, and the filtrate is poured into 20,000 parts of ice-cold water. The yellow solid which precipitates is filtered off, washed with cold water, and dried in air. The resultant product is 1,2,3,4-tetrahydro-2-nitroso-1-phenyl 9H pyrido[3,4 b] indole-3-carboxylic acid.

B. Meso-ionic didehydro 3a,4,9,IO-tetrahydro-IO-phenyl- 1H,3H [l,2,3]oxadiazolo[3',4':l,6]pyrido[3,4 b]- indol-3-one A solution of parts of 1,2,3,4-tetrahydro-2-nitroso- 1-phenyl'9H-pyrido[3,4-b]indole-3-carboxylic acid in 150 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution stirred for 2 hours and then poured into 1700 parts of water. The resultant mixture is stirred for 3 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and washed by trituration in hot methanol to give mesoionic didehydro 3a,4,9,IO-tetrahydro-lO-phenyl 1H,3H- [1,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indol 3 one melting at 228230 with decomposition.

C. Dimethyl 9,10-dihydro 10 phenyl 4H pyrazolo- [1,5': 1,6]pyrido [3,4-b]indole-2,3-dicarboxylate A suspension of 12 parts of meso-ionic didehydro 3a, 4,9,IO-tetrahydro-10-phenyl-1H,3H [1,2,3] oxadiazolo [3,4:1,6]pyrido[3,4-b]indol-3'one in a mixture of 10 parts of dimethyl acetylenedicarboxylate with 100 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 3 hours, whereupon solvent is removed by vacuum distillation and the residue chromatographed on silica gel. From an eluate comprising 10% ethyl acetate in benzene, on evaporation of solvent and recrystallization of the residue from a mixture of acetone and n-pentane, dimethyl 9,10-dihydro-l0-phenyl-4H-pyrazolo[1,5':l,6]pyrido[3,4-b]indole 2,3 dicarboxylate melting at approximately 225226 is obtained. The product has the formula 8 EXAMPLE 9 A. l-(p-chlorophenyl)-1,2,3,4-tetrahydro-2-nitroso- 9H-pyrido [3,4-b] indole-3-carboxylic acid Substitution of 490 parts of l-(p-chlorophenyl)-1,2,3, 4-tetrahydro-9H-pyrido[3,4-b]indole 3 carboxylic acid for the 1,2,3,4-tetrahydro-1-phenyl-9H-pyrido[3,4-b]indole-3-carb0xylic acid called for in Example 8A affords, by the procedure there detailed, 1-(p-chlorophenyl)-1,2, 3,4 tetrahydro 2 nitroso-9H-pyrido[3,4-b1indole-3-carboxylic acid.

BiMeso-ionic didehydro 10-(p-chlorophenyl)-3a,4,9,10- tetrahydro 1H,3H [1,2,3]oxadiazolo[3',4':1,6]-pyrido[3,4-b]indole-3-one.

Substitution of 39 parts of l-(p-chlorophenyl)-1,2,3,4- tetrahydro 2 nitroso 9H-pyrido-[3,4-b]indole-3-carboxylic acid for the l,2,3,4-tetrahydro-2-nitroso-l-phenyl- 9H-pyrido[3,4-b]indole-3-carboxylic acid called for in Example 8B afiords, by the procedure there detailed, meso-ionic didehydro 10 (p-chlorophenyl) 3a,4,9,10- tetrahydro 1H,3H[1,2,3]oxadiazolo[3,4:1,6] pyrido [3,4-b]indol-3-one melting at 224-226 with decomposition.

C. Dimethyl 10(p-chlorophenyl)-9,10-dihydro-4H-pyrazolo[1',5': 1,6] pyrido [3,4-b] indole-2,3-dicarboxylate A suspension of parts of meso-ionic didehydro 10-(p-chlorophenyl)-3a,4,9,10 tetrahydro 1H,3H-[1,2, 3]oxadiazolo[3',4:1,6]pyrido[3,4-b]indol 3 one in a mixture of 70 parts of dimethyl acetylenedicarboxylate with 1000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 3 hours, whereupon it is mixed with decolorizing charcoal and filtered. The filtrate is freed of solvent by vacuum distillation; and the residue is chromatographed on silica gel, using benzene and ethyl acetate as developing solvents. From an eluate comprising 10% ethyl acetate in benzene, on evaporation of solvent and recrystallization of the residue from a mixture of acetone and n-hexane, dimethyl IO-(p-chlorophenyl) 9,10 dihydro 4H pyrazolo[1,5:1,6]pyrido- [3,4-b]indole-2,3-dicarboxylate melting at approximately 233-234 is obtained. The product has the formula ii N coocrn -oooon,

EXAMPLE 1() A. l-(m-bromophenyl)-1,2,3,4-tetrahydro-9H- pyrido [3,4-b] indole-3-carboxy1ic acid Substitution of 814 parts of m-bromobenzaldehyde for the cyclohexane-carboxaldehyde called for in Example 5A affords, by the procedure there detailed, l-(m-bromophenyl)-1,2,3,4 tetra-hydro 9H pyrido[3,4-b]indole- 3-carboxylic acid.

B. l-(m-bromophenyl)-1,2,3,4-tetrahydro-2-nitroso- 9H-pyrido[3,4-b]indole-3-carboxylic acid Substitution of 572 parts of 1-(m-bromophenyl)-1,2, 3,4 tetrahydro-9H-pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4-tetrahydro-1-phenyl-9H-pyrido[3,4-b]indole-3-carboxylic acid called for in Example 8A affords, by the procedure there detailed, 1-(m-bromophenyl)- 400 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 17 parts of sodium nitrite in 35 parts of water. The resultant solution is mixed With decolorizing charcoal, the mixture is filtered through diatomaceous earth, and the filtrate is stirred into 3000 parts of water. The yellow solid which precipitates is filtered ofl, washed with water, and dried in air. The product thus isolated is 1-benzyl-1,2,3,4 tetrahydro 2- nitroso --9H pyrido[3,4 b] indole 3 carboxylic acid.

B. Meso ionic didehydro 10 benzyl 3a,4,9,10-tetrahydro 1H,3H [1,2,3]oxadiazolo]3,4':1,6]pyrido[3, 4-b]indole3-one A solution of 65 parts of l-benzyl-1,2,3,4-tetrahydro-2- nitroso-9H-pyrido[3,4-b]indole-3-carboxylic acid in 300 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution is stirred for 2 hours and then poured into 2500 parts of water. The resultant mixture is stirred for 4 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and recrystallized from methanol to give meso-ionic didehydro 10 benzyl 3a,4,9,10 tetrahydro 1H,3H- [1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4 b]indol 3 one melting at 215-2l7 C. Dimethyl 10-benzyl-9,10-dihydro-4H-pyrazolo- [1,5': 1,6] pyrido[3,4-b]indole-2,3-dicarboxylate A suspension of 22 parts of meso-ionic didehydro 10- benzyl 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo[3',4':1,6] pyrido[3,4 b]indol-3-one in a mixture of 11 parts of dimethyl acetylenedicarboxylate with 200 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 8 hours, whereupon solvent is removed by vacuum distillation and the residue recrystallized from a mixture of acetone and n-pentane to give dimethyl 10-benzyl-9,l0 dihydro 4H pyrazolo[ 1', ':l,6]pyrido[3,4-b]indole-2,3-dicarboxylate melting at approximately 206-207. The product has the formula I N #:000011 000cm EXAMPLE l4 -benzyl-9,10-dihydro-4H-pyrazolo[ 1',5 1,6] -pyrido [3,4-b]indole-2,3-dicarboxylic acid A mixture of 80 parts of dimethyl l0-benzyl-9,10-dihydro 4H pyrazolo-[1,5':1,6]pyrido[3,4-b]indole-2,3- dicarboxylate with 1000 parts of methanol and a solution of 60 parts of potassium carbonate in 250 parts of water is heated at the boiling point under reflux for 4 hours and then poured into 5000 parts of cold water. The resultant solution is stirred with decolorizing charcoal and then filtered. The pH of the filtrate is adjusted to 4 with dilute hydrochloric acid, precipitating a crystalline solid which, filtered off, washed with water, dried in air, and recrystallized from methanol, affords 10-benzy1-9,10-dihydro 4H pyrazolo-[1',5':1,6]pyrido[3,4-b]indole-2,3-

12 dicarboxylic acid melting at 226228. The product has the formula i -COOH EXAMPLE 15 A. 1,2,3,4 tetrahydro 1-(a -methylbenzyl)-2-nitroso-9H- pyrido[3,4-b]indole-3rcarboxylic acid To a suspension of 490 parts of 1,2,3,4-tetrahydro-1-(amethylbenzyl) 9H-pyrido[3,4-b]indole-3-carboxylic acid in 3000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of parts of sodium nitrite in 250 parts of water.- The resultant solution is mixed with decolorizing charcoal, the mixture is filtered through diatomaceous earth, and the filtrate is stirred into 3000 parts of water. The yellow solid which precipitates is filtered off, washed with water, and dried in air. The product thus isolated is 1,2,3,4-tetrahydro-l-(a-methyb benzyl) 2 nitroso 9H-pyrido[3,4-b]indole-3-carboxylic acid.

B. Meso-ionic didehydro 3a,4,9,10-tetrahydro-10-(amethylbenzyl) 1H,3H [1,2,3]oxadiazolo[3',4:1,6] pyrido [3,4-b] indol-3-one A solution of 65 parts of 1,2,3,4-tetrahydro-l-(a-methylbenzyl) 2-nitroso-9H-pyrido [3,4-b]indole-3-carboxylic acid in 3000 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution is stirred for 2 hours and then poured into 2500 parts of water. The resultant mixture is stirred for 4 hours, at which point insoluble solids are filtered out, washed on the filter with water, dried in air, washed by slurry in hot methanol, and again dried in air to give meso-ionic didehydro 321,4,9, IO-tetrahydro-IO- (ct-methylbenzyl) -1H, 3H [1,2,3]oxadiazolo[3,4':1,6]pyrido[3,4 b]indol-3- one melting at approximately 237-238".

C. Dimethyl 9,10 dihydro-10-(ix-methylbenzyl)-4H-pyrazolo[1',5:l,6]pyrido[3,4 b]indole 2,3 dicarboxylate A suspension of 100 parts of meso-ionic didehydro 3a,4, 9,10 tetrahydro-10-(a-methylbenzyl)-1H,3H-[1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4-b]indo1-3-one in a mixture of 57 parts of dimethyl acetylenedicarboxylate with 1000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 5 hours, whereupon solvent is removed by vacuum distillation and the residue chromatographed on silica gel. From an eluate comprising 10% ethyl acetate in benzene, on evaporation of solvent and recrystallization of the residue from a mixture of acetone and n-pentane, dimethyl 9,10-dihydro-10-(oz-methylbenzyl) 4H pyrazolo[1',5': 1,6]pyrido[3,4 b]indole-2,3-dicarboxylate melting at approximately 156 is obtained. The product has the formula 1 3 EXAMPLE 16 9,10 dihydro 10 (a methylbenzyl)-4H-pyrazolo-[1', 5 1,6] pyrido [3,4-b] indole-2,3-dicarboxylic acid Substitution of 85 parts of dimethyl 9,10-dihydro--(amethylbenzyl) 4H pyrazolo[l,5': l,6]pyrido[3,4-b]indole-2,3-dicarboxylate for the dimethyl l0-benzy1-9,10-di hydro 4H-pyrazolo[l,5': 1, 6] pyrido[3,4-b]indole-2,3-dicarboxylate called for in Example 14 afiords, by the procedure there detailed, 9,10*dihydro-IO-(a-methylbenzyl)- 4H pyrazolo [1',5': l,6]pyrido[3,4 b]indole-2,3-dicarboxylic acid melting at approximately 263-264". The product has the formula HCCHa EXAMPLE 17 A. 1,2,3,4-tetrahydro-1-diphenylmethyl-9H-pyrido [3,4-b 1 indole-B-carboxylic acid Substitution of 860 parts of diphenyl acetaldehyde for the cyclohexane-carboxaldehyde called for in Example 5A affords, by the procedure there detailed, 1,2,3,4-tetrahy dro 1 diphenylmethyl 9H pyrido[3,4-b]indole-3-carboxylic acid melting at approximately 197-198.

B. l,2,3,4 tetrahydro 2-nitroso l-diphenylmethyl-9H- pyrido 3,4-b] indole-3-carboxylic acid To a suspension of 50 parts of l,2,3,4-tetrahydro-l-diphenylmethyl-9H-pyrido[3,4-b]indole-3-carboxylic acid in 350 parts of acetic acid at is added, during 30 minutes with stirring, a solution of 10 parts of sodium nitrite in parts of water. Stirring is continued minutes longer, whereupon the resultant solution is treated with decolorizing charcoal and filtered. The filtrate is poured into 2000 parts of ice-cold water, precipitating a yellowish solid which is filtered off, washed with cold water, and dried in air to give 1,2,3,4-tetrahydro-2-nitroso-l-diphenylmethy1-9H-pyrido[3,4-b]indole-3-carboxylic acid melting at 189-191.

C. Meso-ionic didehydro 3a,4,9,IO-tetrahydro-lO-diphenylmethyl 1H,3H [1,2,3]oxadiazolo[3',4':1,6]Pyrido[3,4-b]indol-3-one A solution of 50 parts of 1,2,3,4-tetrahydro-2-nitroso- 1 diphenylmethyl 9H pyrido[3,4-b] indole 3 carboxylic acid in 250 parts of acetic anhydride is heated to 55, whereupon precipitation occurs and heating is discontinued. The resultant solution is stirred for 2 hours, then poured into 2000 parts of water. Stirring is resumed for 3 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and recrystallized from methanol to give meso-ionic didehydro 3a,4,9,10- tetrahydro 10 diphenylmethyl 1H,3H [1,2,3]oxadiazolo[3',4:1,6]pyrido[3,4 b]indol 3 one melting at 243-245 with decomposition.

D. Dirnethyl 9,lO-dihydro-10-diphenylmethyl-4H-pyrazolo[1,5: 1,6] pyrido 3 ,4-b] indole-2,3-dicarboxylate A suspension of 157 parts of meso-ionic didehydro 3a,4 9,10 tetrahydro 10 diphenylmethyl 1H,3H- [1,2,3]oxadiazolo [3',4':1,6]pyrido[3,4 b]indol 3- one in a mixture of 67 parts of dimethyl acetylenedicarboxylate with 2000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 5 hours, whereupon solvent is removed by vacuum distillation and the residue recrystallized from a mixture of acetone and n-pentane to give dimethyl 9,IO-dihydro-10-diphenylmethyl 4H pyrazolo[l',5': 1,6] pyrido[3,4 b]indole 2,3- dicarboxylate melting at approximately l94194.5. The product has the formula EXAMPLE 18 9, 10-dihydro-10-diphenylmethyl-4H-pyrazolo- 1',5': 1,6] pyrido 3,4-b indole-2,3-dicarboxylic acid To a suspension of 97 parts of dimethyl 9,10-dihydro- 10 diphenylmethyl 4H pyrazolo[1,5:1,6]pyrido[3, 4-b]indole-2,3-dicarboxylate in 1000 parts of methanol is added a solution of 60 parts of potassium carbonate in 250 parts of water. The resultant mixture is heated at the boiling point under reflux for 4 hours, then poured into 5000 parts of cold Water. The solution which eventuates is stirred with decolorizing charcoal and filtered. The pH of the filtrate is adjusted to 4 with dilute hydrochloric acid, inducing precipitation of a crystalline solid which is isolated by filtration, washed with water, dried in air, and recrystallized from methanol to give 9,10-dihydro-l0 diphenylmethyl 4H pyrazolo[1',5:1,6]pyrido[3,4 b]- indole-2,3-dicarboxylic acid melting at approximately 235- 236. The product has the formula What is claimed is: 1. A compound of the formula R H I N N-NO COOH References Cited FOREIGN PATENTS 8/1963 Canada.

OTHER REFERENCES Wieland et al., Chemical Abstracts, vol. 51, par. 7370-h to 7372-h. (1957).

Leonard, Chemical Abstracts, vol. 58, par. 12,521-h to 12,522-d (1963).

HENRY R. J ILES, Primary Examiner A. L. ROTMAN, Assistant Examiner U.S. Cl. X.R. 

